Note: This bug is displayed in read-only format because
the product is no longer active in Red Hat Bugzilla.
RHEL Engineering is moving the tracking of its product development work on RHEL 6 through RHEL 9 to Red Hat Jira (issues.redhat.com). If you're a Red Hat customer, please continue to file support cases via the Red Hat customer portal. If you're not, please head to the "RHEL project" in Red Hat Jira and file new tickets here. Individual Bugzilla bugs in the statuses "NEW", "ASSIGNED", and "POST" are being migrated throughout September 2023. Bugs of Red Hat partners with an assigned Engineering Partner Manager (EPM) are migrated in late September as per pre-agreed dates. Bugs against components "kernel", "kernel-rt", and "kpatch" are only migrated if still in "NEW" or "ASSIGNED". If you cannot log in to RH Jira, please consult article #7032570. That failing, please send an e-mail to the RH Jira admins at rh-issues@redhat.com to troubleshoot your issue as a user management inquiry. The email creates a ServiceNow ticket with Red Hat. Individual Bugzilla bugs that are migrated will be moved to status "CLOSED", resolution "MIGRATED", and set with "MigratedToJIRA" in "Keywords". The link to the successor Jira issue will be found under "Links", have a little "two-footprint" icon next to it, and direct you to the "RHEL project" in Red Hat Jira (issue links are of type "https://issues.redhat.com/browse/RHEL-XXXX", where "X" is a digit). This same link will be available in a blue banner at the top of the page informing you that that bug has been migrated.
DescriptionMarcel Apfelbaum
2016-08-09 17:26:21 UTC
+++ This bug was initially created as a clone of Bug #1365613 +++
The virtio 1.0 devices need 8MB MMIO space while SeaBIOS(OVMF?) reserves only 2MB.
The reason the firmware reserves 'only' 2MB MMIO is because it is the minimum allowed by the PCI Spec. It will be unreasonable to default in firmware to a larger MMIO window because it is related only 2 virtio. What about assigned devices that may need more?
I propose the following solution. Add a mmio-window-size parameter to pci bridges and pass all the information to firmware using a para-virt channel like fwconfig.
The firmware can use this info to increase the mmio range for our devices.
We can default the mmio-window-size to 8MB for PCIe ports (which are seen by the firmware as PCI bridges). This will allow hot-plugging virtio-1 devices into PCIe ports with no problem.
Regarding the legacy pci-bridges, the default size is not so clear. I propose to
leave it as is with the following reasoning: On pc 'legacy' machines it is likely we don't need to hotplug virtio-1 'modern' devices, just hotplug virtio 0.9 devices instead.
Side-note:
Some guests, Linux for example, will try to re-balance the PCI root bus MMIO space and assign to pci-bridges/pcie-ports more memory space. Sometimes the guest OS will succeed and sometimes not.
The issue has been solved in upstream QEMU, with a QEMU-only patch. The QEMU item is tracked by clone-origin bug 1365613, so I'm closing this one as a duplicate thereof.
*** This bug has been marked as a duplicate of bug 1365613 ***